It has heretofore been proposed to provide a plastic closure for a container, which comprises a plastic cap or shell with an interior liner for sealing engagement with a sealing surface of the container finish. For example, U.S. Pat. No. 4,984,703 discloses a plastic closure that comprises a shell having a base wall with a peripheral skirt and an internal thread for securing the closure to a container finish, and a sealing liner compression molded in situ on the interior of the shell base wall. U.S. Pat. No. 5,451,360 discloses a method and apparatus for compression molding the liner in situ within the closure shell. It has also been proposed to provide plastic resin barrier materials within the sealing liner for resisting transmission of gases (e.g., carbon dioxide and oxygen), water vapor and/or flavorants through the liner. For example, U.S. Pat. No. 6,371,318 discloses a plastic closure and method of manufacture in which the liner is compression molded in situ on the interior surface of the closure base wall, and includes a multiplicity of alternating layers of matrix polymer such as EVA and barrier polymer such as EVOH. U.S. Pat. No. 6,399,170 discloses a plastic closure and method of manufacture in which the liner is compression molded in situ on the interior surface of the closure base wall, and includes a dispersion of barrier polymer platelets, such as EVOH, dispersed within matrix polymer such as EVA.
It is desirable to provide a closure and liner construction, a method of closure manufacture, and a closure and container package that are particularly well adapted for high-temperature applications. Such high-temperature applications include, for example, applications in which the container is filled with product while the product is hot, such as so-called hot fill and asceptic fill applications. High-temperature applications also include applications in which the filled package is subjected to pasteurization or retort after filling. During retort applications, for example, the filled package may be subjected to a temperature of 265° F. for fifteen minutes. High-temperature situations can also occur when a package is filled with a carbonated beverage and subjected to storage under high-temperature conditions, in which the internal pressure within the container can increase dramatically. In all of such high-temperature situations, the container closure is subjected to elevated internal pressure, which tends to distort or dome the closure base wall and lift the sealing liner away from sealing engagement with the container finish.
Copending U.S. application Ser. No. 09/994,554, filed Nov. 27, 2001 and assigned to the assignee of the present application, discloses a plastic closure that has particular utility for such high temperature and retort applications. The closure includes a shell having a base wall and a skirt with one or more internal threads for securing the closure to a container finish. In some embodiments, a plastic disk is loosely captured within the closure shell. An annular ring extends axially from the disk adjacent to but spaced from the periphery of the disk. A resilient liner is molded onto the disk over at least the central portion of the disk and over the ring on the disk. The ring urges the liner into sealing engagement with the radially inner edge and the axial end of the container finish when the closure is secured to the container finish. In some embodiments of the closure disclosed in the copending application, the disk includes an annular rib around the periphery of the disk, with the liner extending around the inner periphery of the rib. The disk thus urges the liner into sealing engagement with the inner and outer edges of the container finish as well as the axial end of the container finish. When a filled package that includes such a closure is subjected to elevated temperatures, during retort applications for example, the liner is maintained in sealing contact with the container finish.
Although the closure, package and method of manufacture disclosed in the noted copending application address and overcome problems theretofore extant in the art, further improvements remain desirable. In particular, in embodiments in which the liner is disposed on a separate disk retained within the closure shell, there are concerns associated with potential accumulation of debris and/or liquid product in the space between the disk and the base wall of the closure shell, which can promote growth of mold or other undesirable matter. It is therefore a general object of the present invention to provide a closure, a closure and container package, and a method of manufacture that include facility for flushing the area between the closure shell and the liner disk after the closure has been assembled to the container.